Passive infrared detectors have been used to control lights and other electrical appliances. Such devices detect the change in the infrared radiation (heat) within an area and activate the electrical appliance or sound an intrusion alarm. Typically, the change in heat results from a person entering or moving within the sensing area. The appliance remains turned on for a predetermined period of time after which, if no further change in the infrared pattern has occured, the appliance goes off.
One such device is described in my U.S. patent application Ser. No. 714,510 filed on Mar. 21, 1985. That device includes a single pole-double throw switch with a center off position which is typically mounted on the enclosure containing the IR detector electronics. This switch selects one of two modes of operation: (1) automatic, with the IR detector controlling the appliance, or (2) the always-on mode, in addition to an off state.
It is desired to use this type of device to control an electric light which is hardwired in a home, such as an outdoor porch light. Such a light is typically controlled by a single pole-single throw wall switch or two "3-way" switches inside the house. If the IR device is to be added to an existing porch light, the mode control switch would be located outside and the existing wall switch would merely turn the device on and off with no mode control. The operator would have to go outside to select between the automatic and always-on mode. To substitute the mode control switch for the wall switch would require running additional wires. This substitution would not be possible in a "3-way" circuit.
The present invention povides an improved electrical controller that permits the mode control from existing building switches and wiring.